Studies are proposed to identify and characterize cellular mechanisms through which polypeptide hormones and cyclic nucleotodes regulate cell growth and differentiated function. Functional bovine adrenocortical cell cultures are utilized to characterize and quantitate factors which stimulate and inhibit cell proliferation. Because these cells have a finite life span, the changes in cell surface receptors for ACTH, fibroblast growth factor, and angiotensin II, three peptides which control either cell proliferation or differentiated function, will be quantitated. Studies of the intracellular mediators of cyclic nucleotide action, the cyclic nucleotide-dependent protein kinases, will be further characterized. A comparison of cAMP- and cGMP-dependent protein kinase is the major goal. Studies will include determination of partial sequence for comparison, immunological crossreactivity studies, and studies of the biosynthesis and processing of the two cyclic nucleotide-dependent protein kinases in the cell. Moreover, studies are designed to characterize substrates which are important in the regulation of cell function.